Field of the Invention
The present invention relates to a touch panel structure including a color filter, a method for manufacturing the touch panel structure, and a method for manufacturing a display apparatus, and more particularly to a touch panel structure suitable for outdoor use.
Description of the Background Art
In display apparatuses including touch panels used outdoors, excellent display characteristics are demanded also in environments in which incident light amounts from outside the display apparatuses are high, such as use under sunlight. In other words, as a characteristic of touch panel wiring, low reflection to incident light from outside the display apparatus, and high transmission to light from a light source for display are demanded. On the other hand, electrically low resistance is also demanded because of responsiveness, sensitivity, or the like as a touch sensor required for a touch panel.
Furthermore, formation of a touch panel on a first main surface opposite to a color filter formed on a second main surface on the same substrate, namely, an on-cell touch panel is implemented, so that the module thickness of a whole apparatus can be reduced compared to a case where a touch panel substrate is separately provided. Therefore, a display apparatus using the on-cell touch panel is effective to function improvement by thickness reduction and weight reduction, and cost reduction by simplification of a structure.
Therefore, International Publication No. 2011/065292 discloses a touch panel structure, in which a touch panel is formed on a first main surface opposite to a color filter formed on a second main surface on the same substrate, a transparent conductive film having relatively high resistance compared to metal, but having low reflection to incident light from outside a display apparatus and high transmission to light from a light source for display is used as a wiring line in a display part, a metal material such as aluminum having lower resistance than the transparent conductive film is used as a lead-out wiring line or a connection terminal part for outputting an electrode potential of the touch panel to an external circuit board, and a method for manufacturing the same.
On the other hand, International Publication No. 2011/052392 describes a touch panel structure, in which a touch panel is formed on a first main surface opposite to a color filter formed on a second main surface on the same substrate, a metal film low in resistance is used as a wiring line, and which is disposed at an overlapping position in a display panel thickness in a portion other than an openings in a pixel part so as not to shield light form a light source for display, and a method for manufacturing the same.
Furthermore, Japanese Patent Application Laid-Open No. 2013-222123 describes a touch panel structure used in touch panel wiring having an antireflection function formed of an aluminum film, an aluminum nitride film (low reflection film), and a transparent film, as an example, for the purpose of disposing an antireflection film on an aluminum alloy wiring line, in order to reduce reflection of incident light from outside a display apparatus, and a method for manufacturing the same.
However, the touch panel structure disclosed in International Publication No. 2011/065292 is complicated, and has a problem that the transparent conductive film of the display part is still high in resistance, and particularly, excellent electrical characteristics are not obtained to increase in size (increase in size of a screen).
The touch panel structure disclosed in International Publication No. 2011/052392 has a problem that since placement of the touch panel wiring needs to match a light shielding layer of the color filter or the like, restriction on design is large.
On the other hand, in the touch panel structure disclosed in Japanese Patent Application Laid-Open No. 2013-222123, since the wiring line is low in resistance, a wiring line width can be designed thinner, a high opening ratio is attained and optical characteristics and electrical characteristics demanded for a touch panel, described before, are sufficiently satisfied.
However, in a case where the touch panel using the Al (aluminum) based low reflection wiring line is formed on the substrate as disclosed in Japanese Patent Application Laid-Open No. 2013-222123, when a case of performing a step of forming the color filter on a surface opposite to the substrate after that is assumed, there is a problem that a metal portion functioning as the connection terminal part provided in the opening of the touch panel wiring line is damaged by an alkaline developer used in a step of developing the color filter, and connection failure between the connection terminal part and the wiring line is generated.
On the contrary, when a case of first forming the color filter on the substrate, and thereafter performing a step of forming the touch panel structure disclosed in Japanese Patent Application Laid-Open No. 2013-222123 is assumed, the color filter is already formed on the lower surface of the substrate when the touch panel structure is formed, and therefore there is a problem that the color filter is damaged during stage absorption such as exposure or conveyance, which is performed in the step of forming the touch panel structure, and a yield is lowered.